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Anionic 3 + 2 Cycloaddition of 2-Azaallyllithium Compounds to CN and NN Double Bonds.

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W e have found t h a t a-2-acetoxyethyl- ( l b ) [7,81 a n d a-2-acetoxypropylbis(biacety1dioximato)pyridinecobalt ( l c ) [7,81
a r e c om pounds o f extraordinary solvolytic reactivity.
T he ir hydrolysis, methanolysis, a n d ethanolysis occur
a t 25'C with half-lives o f a few hours. High yields of
products from these reactions have been isolated a n d identified a s alcohols [e.g. f I a ) f r o m ( I b ) ] f r o m hydrolysis a n d
significantly ethers f r o m alcoholysis. Th u s, methanolysis of
( I b ) gave t h e methyl ether ( I d ) [XI. Ethanolysis of ( I b ) gave
( l e ) , which was identified by comparison with a samp l e
prepared by independent synthesis [I].
G o o d first-order kinetics 191 were observed f o r th e solvolysis
of ( l b ) in a bs olute eth an o l a t 25 "C [ k = 4.37 4- 0.06 x 10-6
s-1, Ea == 19.9 '- 1.2 kcal . mole-I, AS* = -18.2 .'- 4.2 cal .
deg-1 mole-I]. Ethanolysis of ( l c ) gave (117 (81 a t a rate 20
times faster a t 25 'C t h a n t h e r a t e for (16). Th ese values
should be compared with d a t a for o th er so ~v o ly tical l yreactive acetatesrlol: ( I b ) a n d ( I c ) a r e o f comparable reactivity
t o trityl acetate! F ur th er m o r e, ethanolysis of ( l b ) in ethanol
[ * ] Dr. B. T. Golding, H . L. Holland, Dr. U . Horn, and
S . Sakrikar
School of Moleculai- Sciences, University of Warwick
Coventry CV4 7AL (England)
I*']We thank the Science Research Council for the award of
an M.Sc. studentship to H. L. H., theschweizerischer Nationalfonds for the award of a Postdoctoral Fellowship to U . H . tinder
the European Exchange scheme and the British Council, Apte
Educational Trust, and Dorabji Tata Trust for awards to S.S.
[ I ] G. .V. Schrauzrr and R. J . Windgnsserr, J. Amer. Chem. SOC.
89, 143 (1967); G. N . Sclrraiizer, Accounts Chem. Res. I , 97
(1968).
[2] The possible existence of alkene-cobalamin complexes has
been discussed by M . L . H. Green in G. E . Coutes, M . L . H .
Green, and K. Wade: Organometallic Compounds, Methuen.
London, 1968, Vol. 2, p. 249, i n the context of the analogous
acid-induced decomposition of 2-hydroxyethylcobalamin.
[3] (Sa), (3b), and (3c) would be new types of olefinic complex having an alkene bound to a metal (CoIlr) within a ligand
system assumed to remain approximately planar. Th e bonding
between alkene and cobalt in (3a) can be visualized through
the Chatt-Duncanson model [4a]. f36) is represented as a
primary carbonium ion, but is expected to be stabilized by
overlap with neighboring orbitals ( i . e . filled dxr and dyr of C o
and/or bonding n-levels of biacetyldioxime). (3c) is based on
hyperconjugation [4b, c] i.e. the carbonium
the concept of a--TC
ion center is stabilized only by overlap with the Co-CI a-bond
and there is no displacement of C o towards the electron deficient carbon atom as in (30) and possibly 136).
[4] a) E. 0. Fischer and H. Werner: Metal x-Complexes.
Elsevier, Amsterdam 1966, Vol. 1, Chapter 111; b) T.G. Traylor
and J . C . Ware, J . Amer. Chem. SOC.89, 2304 (1967); c) W.
Hanstein, H. J . Berwin, and T . G. Traylor, ibid. 92, 829 (1970).
[5] Hereinafter, ( 3 ) will refer t o the intermediate whose actual
structure may be (3a), (361, or (3c).
161 G. Gokel, P . Hogmann, H . Klusacek, D . Marquarding, E.
Ruch, and I. Ugi,Angew. Chem. 82, 77 (1970); Angew. Chern.
internat. Edit. 9, 64 (1970), and references cited therein; R. S .
BIy and R. L . Venzey, J . Amer. Chem. SOC.Y I , 4221 (1969), and
references therein.
[71 (16) and ( I c ) were prepared by acetylation (acetic anhydride/pyridine/room temperature136 h) of ( l a ) and l l g ) respectively.
[8] New compounds gave satisfactory combustion analyses for
C , H, and N and spectroscopic data (IR, UV, and N M R )
consistent with their assigned structures.
[9] Reactions were sealed and thermostated i n darkness.
Their extent was assayed by N M R spectroscopy of aliquots.
[lo] Cf. E . A . Hilland J . H . Richards, J. Amer. Chem. SOC.83,
3840 (1961).
[ I l l G. N . Sclzrauzer and R . J . Windgassen, J. Amer. Chem.
Soc. 89, 1999 (1967).
1121 W . Kitching, Organomet. Chem. Rev. 3, 61 (1968) and
references cited therein.
[13] M . M. Kreevoy and G. B. Bodem, J. Org. Chem. 27, 4539
(1962).
[14] J . Hulpern and H. B. Tinker, J. Amer. Chem. SOC.89,
6427 (1967).
960
saturated with propene an d o f ( I c ) in et h an o l sat u r at ed
with ethylene gave n o crossed products [e.g. ( l e ) from ( I c ) ] ,
thereby eliminating a fragmentation-recombination mechan i sm f r o m consideration. T h e a-vinyl c o m p o u n d is n o t a n
intermediate, because alcoholysis o f ( l b ) in [D4]-methanol
gave ( I d ) containing deuterium only in t h e methoxy group
of t h e side-chain.
These results a r e in accord with a mechanism in which
ionization o f ( I b l to ( 3 ) a n d o f ( I c ) t o methyl-substituted
( 3 ) is rate-determining followed by cap t u r e of these intermediates by solvent. A smal l a m o u n t of leakage occurs t o
give dealkylated products [e.g. f 2 b ) in hydrolysis] presumably by loss of ethylene from 1.3) giving coordinatively unsaturated CoTIf which reacts with solvent. A similar mechanism applies t o the decomposition of ( l a ) in t h e presence
of acid, except that t h e reaction is now equilibriumcontrolled a n d lcads to products of type (2) exclusively.
Th e appreciable negative entropy of activation observed
for ethanolysis of ( I b ) suggests t h at in ( 3 ) there is restriction o f rotation ab o u t t h e C - - - C b o n d o f the CH*-CHz
unit, which would be expected of an y of t h e suggested
structures for (.?I.
Further evidence for t h e intermediacy of methyl-substituted
(31 was o b t ai n ed by carrying o u t hydrolysis o f ( l c ) in dio x an e water (1 :1) in t h e presence of NaBH4 ( 3 eqvts. / ca.
5 "C i 90 min). In ad d i t i o n t o t h e alcohol (1s) a n d products
derived from reductive cleavage o f t h e Co-C bond, 10%
of the a-propyl derivative was f o r med (identified by co mparison with a samp l e prepared in the st an d ar d way[11]).
resembles
T h e acid-promoted decomposition of ( l a )
t h e acid-catalyzed deoxymercuration o f 2-hydroxyalkylmercury(I1) derivatives'l21, whilst t h e solvolyses of ( I b )
a n d (Ic) bear similarity t o t h e neutral solvolytic chemistry
o f 2-acetoxyethylmercuric iodide [131. T h e reactions of t h e
mercuric derivatives have long been t h o u g h t t o proceed via
a z-complex of HgIr with alkene (mercurinium ion)[121,
although t h e precise r o l e.an d n at u r e of this species is still
uncertain r4C9 141. 130) corresponds t o a symmetrical
mercurinium ion. However, t h e present system differs
clearly from deoxymercuration in t h at t h e loss o f ethylene
from ( 3 ) is kinetically slower t h a n its cap t u r e by solvent,
whereas in deoxymercuration, t h e co n t r ar y kinetic situation
probably obtains.
Received: September 8, 1970
[ Z 298 1El
German version: Angew. Chem. 82,983 (1970)
+
Anionic 3 2 Cycloaddition of 2-AzaallyUithium
Compounds to CN and NN Double Bonds[ll[**I
By Thomas Knuffmann, Heike Berg, Elisabeth Liidorff; a n d
Annegret Woltermanri 1*I
2-Azaallyllithium co mp o u n d s were recently reported 121 t o
react with olefinic C C double bonds t o give anionic cycload d u ct s t h a t afford pyrrolidines o n hydrolysis with water.
+
W e have n o w observed analogous anionic 3
2 cycloadditionst31 with azomethines an d azo compounds. Th ese reactions, designated (A) a n d (B) i n t h e reaction scheme, t ak e
place when a solution of t h e 2-azaallyllithium co mp o u n ds
( I ) a n d (21123 in T H F / e t h e r (9: 1) is t r eat ed a t -60°C
under nitrogen with a n equimolar a m o u n t of o n e of t he
azomethines or azo co mp o u n d s listed in t h e Tab l e a n d then
warmed. After hydrolysis of t h e reaction mixture with
water t h e respective imidazolidine or 1,2,3-triazolidine
co u l d be isolated. T h e constitution of these apparently
hitherto undescribed co mp o u n d s follows f r o m analyses,
molecular-weight determinations, a n d t h e N M R , IR, a n d
mass spectra
These reactions represent t h e first application o f a new
synthetic met h o d for t h e little-studied class o f imidazolidines 141 a n d 1,2,3-triazoIidines [51.
T h e reactions o f 1,3-diphenyl-2-azaallyllithium(2) with
azomethines or azobenzene, with sh o u l d theoretically yield
Angew. Cheni. internat. Edit.
1 Vol. 9
(1970)
1 No.
12
+
Anionic 3 2 Cycloaddition of a
1,2-Diazaallyllithium CompoundII J [**I
I .i
-
H I,i c&35 - N(,~,
=N)+...A
K Iq H'
(I), R = H
R'=C6H5
(2). R
\
By Thomas K o u f f1~1aiin,Dieter Berger, Bjorn Sclzeercr, and
Annegret Wolferinann[*I
-
/
H{-~:H~
II,O
R
11
Li
I
= Cs€I5
R'= H
It therefore appeared questionable whether 1,2-diazaallyl
anions ( I ) can add to olefinic double bonds as shown in (.C)
since this would involve only slight transfer of negative
Li
2-Azaallyl
cpd.
+
/
The energy barrier to be overcome in anionic 3
2 cycloN-X
additions according to (A) (21 and the corresponding cyclo~ ~ ~ ' 1 ~eliminations
~ H 5
according to (8)(X = 0, S)[31 should be low
since the symmetry of the ~i orbitals is conserved [4+51. The
ir
direction of reaction is dictated by the arrangement o f the
electronegative hetero atoms: The reaction that occurs is
that in which the negative charge is transferred from the
carbon to more electronegative atoms.
\
Yield
( %,)
Temp.
Azomethine or azo cpd.
( "C)
[a1
Product
bl
__
~
2-PyridinecarLpldehydeanil
20
20
20
20
Azobenzene
Azobenzene
p,p'-Azotoluene
3,3'-Azopyridine
20
20
65
65
Benzylideneaniline
Benzylideneaniline
2-Pyridinecarbaldehydeanil
1,2,3,3-Tet raphenyl- 1,2,4- t riazolidine
1,2,3,5-Tetraphenyl-l,2,4-triazolidine
3,3-Diphenyl-l,2-di-p-tolyl-1,2,4-triazolidine
3,3-Diphenyl-1,2-di(3-pyridyl)-l,2,4-triazolidine
43
52
41
54
121-122
111-113
164
153-155
43
50
58
10
139
190-191
139-140
184-186
[a] After addition of the azomethine or the azo compound t o a solution of the lithium compound a t -60 "C the reaction
[bl Yield not optimized.
mixture was slowiy warmed t o the temperature given.
four racemic imidazolidines or gibe one meso and one
racemic 1,2,4-triazolidine, were found to give only one
imidazolidine or triazolidine. The apparent stereospecificity strongly suggests that the cycloaddition of ( 2 ) to C N
and N N double bonds is a concerted process, as predicted
by the Woodward-Hoffmann rules 161.
charge from a carbon to a nitrogen atom because of extensive localization of the negative charge o n the peripheral
nitrogen atom in ( I ) .
It would also appear likely, from the close similarity between the C N and the C O double bond, that the reactions
of 2-azaallyllithium compounds with carbonyl compounds,
which leads to open-chain hydroxy azomethines 171, are
also initiated by a concerted 4;c + 2x cycloaddition and
therefore proceed via a 1,3-oxazolidine-lithium compound.
[Z 299a IEI
Received: October 15, 1970
German version: Angew. Chem. 82, 986 (1970)
.... -.
_.
[ * ] Prof. Dr. Th. Kauffmann, H. Berg, E. Ludorff, and
A. Woltermann
Organisch-Chemisches lnstitut der Universitiit
44 Miinster, Orleansring 23 (Germany)
[**I This work was supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie.
[l] Organo-lithium and -aluminum Compounds, Part 4. Part 3: [2].
[2] Th. Kaufmann, H . Berg, and E. Koppelmann, Angew. Chem.
82, 396 (1970); Angew. Chem. internat. Edit. 9, 380 (1970).
[3] The extremely reactive extra bond of dehydrobenzene is
able to add allylmetal compounds in a kind of 3 + 2 cycloaddition: cf. C. Wittig and E. Knauss, Chem. Ber. 91, 895
(1958); C. F. Huebner and E . M . Donoghue, J. Org. Chem. 33,
1678 (1968); W . T . Ford, R. Radue, and J . A. Walker, Chem.
Commun. 1970, 966.
141 lmidazolidines: cf. R. J . Ferm and J . L . Riebsomer, Chem.
Rev. 54, 606 (1954).
151 1,2,4-Triazolidines: cf. J . Strafing, W . E . Weening, and B.
Zwanenburg, Recl. Trav. Chim. Pays-Bas 83, 387 (1964); 84,
408 (1965).
161 R. B. Woodward and R . Hojjmann, Angew. Chem. 81, 197
(1969); Angew. Chem. internat. Edit. 8, 781 (1969).
171 Th. Kauffmann, E. Koppelmann, and H . Berg, Angew.
Chem. 82, 138 (1970); Angew. Chern. internat. Edit. 9, 163
(1970).
Angew. Chem. internat. Edit.
/ Val. 9 (1970) 1 NO. 12
We have now found that benzeneazomethane ( l a ) undergoes extensive (>88 %) metalation to the hitherto unknown orange-red compound benzeneazomethyllithium (2)
on treatment with 1.1 mol. equiv. of n-butyllithium in
THF/n-hexane (ca. 9 :1) a t -70 "C(61; moreover, the anion
of ( 2 ) , 1,2-diazaallyl anion, is able to add to the anglestrained olefinic double bond of acenaphthylene (according
to (C)). Addition of water t o the reaction mixture yielded
the hydrolysis product /5)[71 of the cycloadduct (4);
treatment with ethyl bromide instead of water gave the dehydrogenation product ( 6 ) (for reaction conditions and
yields, see Table).
A corresponding cycloaddition did not occur with the 1,2bisazaallyllithium compound (3), which is obtained almost
quantitatively as a n orange-red solution (THFln-hexane,
ca. 5 :1) o n reaction of benzaldehyde phenylhydrazone and
one mol. equiv. of n-butyllithium a t -70°C. This finding,
together with the fact that neither (2) nor ( 3 ) could be induced to add to styrene, trans-stilbene, or tolan, confirms
the prediction that 1,2-diazaallyllithium compounds are
less prone t o 3 + 2 cycloaddition than 2-azaallyllithium
compounds (21.
Addition of benzeneazomethyllithium to carbonyl conipounds (see Table) leads - possibly via a n unstable
96 1
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